Selective breeding for desiccation tolerance in liquid culture provides genetically stable inbred lines of the entomopathogenic nematode Heterorhabditis bacteriophora

Abstract

The entomopathogenic nematode (EPN) Heterorhabditis bacteriophora is used in biological plant protection to control pest insects. In the past, several attempts targeted at an enhancement of the desiccation tolerance of EPN by genetic selection in order to improve their storage stability. The subsequent loss of improved beneficial traits after release of selection pressure has often been reported. In order to stabilize progress of selective breeding, selection during liquid culturing was tested against propagation in host insects. After release of the selection pressure, the tolerance was monitored over additional reproductive cycles in vivo and in vitro to compare the stability of the trait. Furthermore, it was tested whether the virulence of the selected strains would be impaired. Exposure to desiccation stress prior to propagation, in vivo or in vitro, both resulted in increasing desiccation tolerance. When selection pressure was released, the gained tolerance was lost again during in vivo production, whereas the tolerance was maintained at a high level when EPNs were cultured in liquid culture. In Heterorhabditis sp., liquid culture conditions produce highly homozygous, genetically stable inbred lines. The investigation provides easily applicable methods to improve and stabilize beneficial traits of heterorhabditid EPNs through selective breeding in liquid culture. Compared to nematodes from in vivo propagation, production in liquid media yielded EPN of higher virulence.

Entomopathogenic Nematode Application Technology

“…Thus, Bai et al, (2005) proposed that EPN producers develop numerous inbred lines from promising candidate populations, and then select the lines that exhibit high levels of desirable traits for commercialization. In a variation of the Bai et al, (2005) approach, Anbesse, Sumaya, Dörfler, Strauch, and Ehlers (2013) reported that multiple heterorhabditid inbred lines can be created during liquid culture. Given that heterorhabditids cannot mate in liquid culture, all progeny are produced by selfing (via hermaphrodites) , which results in automatic creation of multiple inbred lines.…”

Prospects in the Application Technology and Formulation of Entomopathogenic Nematodes for Biological Control of Insect Pests

“…Gaugler & Campbell, 1991;Gaugler, Campbell, & McGuire, 1989;Hiltpold et al, 2010a;Hiltpold, Toepfer, et al, 2010 (Gaugler & Campbell, 1991;Gaugler et al, 1989) or other particular behaviors (Bal, Michel, & Grewal, 2014), virulence (e.g., Peters & Ehlers, 1998;Tomalak, 1994), tolerance to extreme temperatures (e.g., Ehlers, Oestergaard, Hollmer, Wingen, & Strauch, 2005;Shapiro, Glazer, & Segal, 1997;Susurluk, Ulu, & Kongu, 2013) and desiccation (e.g., Anbesse, Sumaya, Dörfler, Strauch, & Ehlers, 2013;Strauch, Oestergaard, Hollmer, & Ehlers, 2004). While selective breeding offers an efficient and relatively quick method to obtain EPN populations with desired or improved traits (discussed in Chap.…”

Nematode Pathogenesis of Insects and Other Pests

“…Despite superior performances, native and adapted EPN populations may still fail in controlling pest populations under harsh conditions in their natural environment. Previous studies have demonstrated that genetic selection of EPNs can overcome certain physiological limitations by improving various traits of particular interest for biological control such as host finding (e.g., or other particular behaviors (Bal, Michel, & Grewal, 2014), virulence (e.g., Peters & Ehlers, 1998;Tomalak, 1994), tolerance to extreme temperatures (e.g., Susurluk, Ulu, & Kongu, 2013) and desiccation (e.g., Anbesse, Sumaya, Dörfler, Strauch, & Ehlers, 2013;Strauch, Oestergaard, Hollmer, & Ehlers, 2004). While selective breeding offers an efficient and relatively quick method to obtain EPN populations with desired or improved traits (discussed in Chap.…”